Electronic devices are in widespread use throughout the world, and portable electronic devices such as cellular radio telephones and personal data organizers are also used in increasing frequency. In many instances people may have several of these devices for performing different tasks. From a user's perspective, it would be much more convenient to have such devices integrated into one device. Integration would eliminate having to maintain separate accessories, batteries, and so on, and carrying one device is more convenient than carrying several devices for separate functions. One problem that has arisen in considering ways to integrate such devices into one device is the ergonomics of the user interface. For example, users have come to expect a cellular radio telephone to have a numeric keypad, with several alphabetic characters available on the digit keys for text entry. Conversely, users of so called two-way pagers and palm-top computers are accustomed to more conventional “QWERTY” keypads, having a layout similar to that of computer keyboards and typewriters.
Manufacturers of electronic devices often manufacture the devices for sale in more than one world market, and consequently often have different keypads or buttons made with language or characters corresponding to the language prevalent in a particular region. This necessitates having an inventory of different parts for keypads and button, as well as maintaining separate “kits” for tracking the devices once they are assembled to assure the right kit goes to the intended market.
It would be of substantial benefit if, on an integrated device that performs several functions, the keypad and buttons could adapt, and change their appearance, so as to provide a familiar interface to the user. Similarly, if a keypad or button could change its appearance, then the same keypad could be used for different language markets, and it would simply display the appropriate characters or symbols. That is, if the keypad was adaptable, a common keypad sub-assembly could be used, thereby eliminating the need for inventorying different keypad parts for different language markets. Having different characters or symbols displayed on various keys or buttons would be possible using conventional display technology, such as liquid crystal displays, one on each button. However this approach suffers from being prohibitively expensive, and currently LCD displays are not flexible enough, so they would not be optimal for use with popple switch type keypads commonly found on portable electronic device. An adaptable keypad and button mechanism for use therewith which is inexpensive and mechanically flexible is described in U.S. Patent Application Publication No. US2003/0058223 A1 to Tracy et al. (“Tracy”) which can be implemented using low power consumption bi-stable displays such as E-ink's electrophoretic display or cholesteric liquid crystal displays. The Tracy keypad is a reflective type display that depends on ambient light for its illumination and thus is not suitable for dark environments. Other commonly practiced keypad lighting schemes are no longer practical due to the low transmittance of these displays. As shown in FIG. 1, these other common keypad lighting schemes 10 have symbols 18 located on an exterior surface of the keypads 16 that protrude through holes in a housing 20. This scheme further includes a metal dome or popple switch 14 and a light source 15 such as an up-facing electroluminescent (EL) film that both reside on a printed circuit board 12 as shown. The light source 15 provides sufficient light from behind the keypads to illuminate such keypad structure. However, when symbols are on display layer that is between the metal dome or popple switch and the clear transparent keys (see FIG. 3), the front or up-facing light source 15 is no longer useful or effective in such structure. Thus, a need exists for providing an adaptive keypad and button mechanism such as the Tracy keypad that can further be illuminated in dark environments.